ClassCastException when trying to use Mirror.Of[T] when T contains a Tuple

[VlachJosef]

Compiler version

3.0.0-RC2
sbt 1.4.9 (GraalVM Community Java 1.8.0_282)

Minimized code

import scala.deriving.*
import scala.compiletime.{erasedValue, summonInline}

case class Simple(a: String, b: Boolean) derives Printable
case class SimpleT(a: (String, Boolean)) derives Printable

@main def hello: Unit = {

  summon[Printable[Simple]].print // Prints STRING BOOLEAN as expected

  summon[Printable[SimpleT]].print // java.lang.ClassCastException: SimpleT$$anon$1 cannot be cast to scala.deriving.Mirror$Product

}

trait Printable[T]:
   def print: Unit

object Printable:

   given Printable[String] with
      def print: Unit = println("STRING")

   given Printable[Boolean] with
      def print: Unit = println("BOOLEAN")

   def printProduct[T](p: Mirror.ProductOf[T], elems: => List[Printable[_]]): Printable[T] =
      new Printable[T]:
         def print: Unit =
            elems.foreach(_.print)

   inline given derived[T](using m: Mirror.Of[T]): Printable[T] =
      val elemInstances = summonAllPrintable[m.MirroredElemTypes]
      inline m match
         case p: Mirror.ProductOf[T] => printProduct(p, elemInstances)

end Printable

inline def summonAllPrintable[T <: Tuple]: List[Printable[_]] =
   inline erasedValue[T] match
      case _: EmptyTuple => Nil
      case _: (t *: ts) => summonInline[Printable[t]] :: summonAllPrintable[ts]

Output

> run
[info] running hello 
STRING
BOOLEAN
[error] (run-main-0) java.lang.ClassCastException: SimpleT$$anon$1 cannot be cast to scala.deriving.Mirror$Product
[error] java.lang.ClassCastException: SimpleT$$anon$1 cannot be cast to scala.deriving.Mirror$Product
[error] 	at SimpleT$.derived$Printable(Main.scala:5)
[error] 	at Main$package$.hello(Main.scala:11)
[error] 	at hello.main(Main.scala:7)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
[error] 	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
[error] 	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
[error] 	at java.lang.reflect.Method.invoke(Method.java:498)
[error] stack trace is suppressed; run last Compile / bgRun for the full output
[error] Nonzero exit code: 1
[error] (Compile / run) Nonzero exit code: 1
[error] Total time: 3 s, completed Mar 31, 2021 9:16:29 PM

Expectation

I'd expect this program to produce compilation error about missing Printable[(String, Boolean)] or similar.

Trying to get familiar with type-classes-supporting-automatic-deriving I'm trying to implement typeclass which prints its own type.

Minimized project is available here.

[bishabosha]

Hi, thank you for opening this issue, I believe that this is the same issue as #11542 so I will close